tankmates

[Bombina Bob]

You can house up to six FBTs successfully in a 20 gallon tank but whenever keeping multiple species of amphibians together, you need a much larger tank than a 20 gallon so they dont come into contact with eachother, there are too many stories about the disasters of keeping FBT and FBN together, i dont suggest mixing species unless they are native to the same area and can cohabitate. Ive kept fish with my FBTs befire though, you can house danios, guppies and mollies with them but your toads may make a snack out of them!

Here's the article on mixing species disasters at Caudata culture
Caudata Culture Articles - Species Mixing Disasters

[Mentat]

Hello and welcome to FF Caden. The idea of creating a little natural set-up with coexisting species is very attractive but impractical. As Ryan stated, they usually end in disasters. Problem is in nature animals come and go, eat each other, fight, run away, etc. In an small enclosure (and 20 L is small for the project) there is very little place to hide and no where to run .